Apollo 16 Mission

Landing Site Overview

"The LM landed in a subdued old crater, approximately 75 meters in diameter. In general, the landing area is saturated with these old craters so that the few young sharp-rimmed craters provide a notable contrast to the pervasiveness of the old craters. In the immediate vicinity of the LM, a few 1- to 2-meter craters have glass-coated bottoms. This glass is cracked and wrinkled so that it looks like dried mud. A low percentage of the surface is covered by subrounded to subangular blocks. To the north, the Turtle Mountain ridge shields the traverse route of the third period of the extravehicular activity. To the south, except between the many 5- to 10-meter ridges, we could see the EVA 2 traverse route as far as station 4. The surface sloped to the south an estimated 100 meters, where a gentle rise marked the beginning of Stone Mountain."

John Young, Thomas Mattingly, and Charles Duke

Landing Site Selection

The Apollo 16 landing site was selected to obtain samples of two highland geologic units, the Descartes Formation and the Cayley Formation, which are widespread on the lunar nearside. Prior to the mission, it was thought that both were of volcanic origin, but the returned samples demonstrated that this is incorrect.

Three of the first four Apollo Moon landings were in mare regions and the fourth was in ejecta from the Imbrium impact. When selecting the Apollo 16 landing site, the highest priority was given to landing at a site in the lunar highlands, which occupy more than five times the surface area occupied by mare units.

Two locations were given primary consideration, the Descartes region west of Mare Nectaris and Alphonsus crater. In Descartes, the objectives were to sample the Descartes Formation and the Cayley Formation. Based on the interpretations of telescopic and orbital imagery, it was thought that both units were volcanic in origin, although formed of magmas that were more viscous than mare lavas. Samples obtained by Apollo 16 proved that these units are actually breccias produced by impacts rather than volcanic features. From the density of impact craters, the Cayley Formation was thought to be comparable in age to the Imbrium impact. These premission geologic studies suggested that these two formations covered about 11% of the lunar nearside, making them important for the overall understanding of the Moon's history. Also, the large distance between the Descartes site and previous landing sites was helpful for the network of geophysical instruments created by the Apollo 12 through 16 missions.

There were three sampling objectives for the Alphonsus crater site: the crater fill itself, possible pre-Imbrium material from the crater wall, and possible young volcanics at some so-called dark halo craters on the floor of Alphonsus. However, some geologists felt that the Alphonsus site had been contaminated by ejecta from the Imbrium Basin impact. Also, at the time the Apollo 16 landing site was selected in June 1971, the Apollo 14 samples had been incompletely analyzed and the Apollo 15 samples had not yet been obtained. It was considered possible that the objective of obtaining samples of old highland material (older than the Imbrium impact) might be met with some of the Apollo 14 or 15 samples.

Accordingly, it was decided that Descartes would be the landing site for Apollo 16. The Alphonsus site was considered at the time to be the primary candidate for the Apollo 17 landing site, although this was later rejected. The Descartes site was certified as safe for landing on the basis of Apollo 14 orbital photography. The specific landing site was selected between two fresh, young impact craters, North Ray Crater (1000 meters in diameter) and South Ray Crater (680 meters in diameter). These craters provided natural drill holes through the regolith at the site, exposing samples of the underlying bedrock in ejecta fragments for sampling by the Apollo 16 crew.

Orbital Views of the Landing Site

Apollo 16 site: Earth-based telescopic view
The arrow points to the landing site in the densely cratered southern highlands. Apollo 16 was the only mission to land in a highland area not directly adjacent to the mare. The two large craters near the middle of the lower margin are Theophilus and Cyrillus. Ejecta from the younger Theophilus Crater may be present in the area of the landing site. (Consolidated Lunar Atlas photograph E9, Lunar and Planetary Laboratory, University of Arizona.)

Apollo 16 site: Oblique view
This low-phase-angle photograph shows the high albedo rays of North Ray and South Ray Craters near the landing site in the lunar highlands. (NASA photograph AS16-2464[M].)

Apollo 16 site: Moderate resolution vertical view
The landing site is on the Cayley Plains, a planar unit that fills in topographic lows throughout this region of the highlands. The Cayley Plains were identified from Earth-based observations as a distinct stratigraphic unit throughout large portions of the highlands. The rugged uplands east and south of the landing site are the Descartes Mountains adjacent to the very degraded Descartes Crater at the lower margin of the photograph. (NASA photograph AS16-0161[M].)

Apollo 16 site: High resolution vertical view
The bright-rayed crater (lower left) is South Ray Crater; ejecta from this crater was sampled by astronauts John Young and Charles Duke during the second EVA, along with material from the lower slopes of nearby Stone Mountain (center of bottom margin), part of the Descartes Mountains. The pair of sharp-rimmed craters directly north of the landing site are Kiva (left) and North Ray (right) Craters. The crew visited the rim of North Ray Crater during the third EVA. (NASA photograph AS16-4558[P].)

Apollo 16 site: Enlargement of high-resolution view
The lunar module casts a distinct shadow on the Cayley Plains. The landing site is about 500 meters east of the rim of Spook Crater, which was visited by the crew during the first EVA. (NASA photograph AS16-4558[P].)

The Apollo 16 landing site (green cross) is on the relatively smooth Cayley Plains, between the two bright ray craters in the center of the stereo pair. The Cayley Plains extend to the west of the rugged Descartes Mountains in the center right and bottom of the scene. These views (portions of Mapping Camera frames AS16-974 and AS16-976) measure ~65 kilometers from top to bottom. North is to the top. This stereo pair has a vertical exaggeration of about 3. Topographic relief across this scene is about 900 meters.

Viewing Instructions

Red/Green (Anaglyph) ImagesTo view anaglyph stereo pairs you need red-green (or red-blue) stereo glasses. These glasses have a red lens over the left eye and green (or blue) lens over the right eye.

Side-by-side stereo pairs can also be viewed with the unaided eye by focusing on each image separately and allowing the eyes to cross. If you wear glasses, it may be necessary to remove them and view the pairs from 6 to 10 inches away. These techniques may require some practice (the Apollo 15, 16 and 17 stereo pairs are good for this purpose). Another means of assisting this process is to place an index card upright between the two images, forcing each eye to see the different images. Only approximately 10% of the general public cannot view images stereoscopically.